The present invention relates generally to composite materials, and more specifically, to metal matrix composites (MMC).
Metal matrix composites include a continuous metallic phase, referred to as the matrix, combined with another phase, the reinforcement, to strengthen the metallic phase and increase high-temperature stability. The reinforcement is typically a ceramic in the form of particulates, platelets, whiskers or fibers.
Metal matrix composites find application in many fields including gas turbine engines. Many metal matrix composites are extremely strong, lightweight, and have significant resistance to extremes in temperature and in temperature changes. The properties associated with metal matrix composites are considered beneficial for application in rotating machinery such as turbo machinery rotors where component hoop stress can be significant.
The fabrication of metal matrix composites involves the placement of the reinforcement between layers of metallic sheet or foil. A stack of the material is then heated and isostatically pressed (HIP) or vacuum hot pressed (VHP) into a composite. One prior approach of laying up the material for the stack is to weave the reinforcing material into mats which are then located between the layers of metallic sheet or foil. Utilization of mats in fabricating metal matrix composites has generally required significant consolidation, that is, reduction in overall volume, when the composite is processed to its ultimate shape. The resulting metal matrix composite generally has a lower strength because of the lack of desired orientation in the reinforcement. An approach utilized to reduce the degree of consolidation in forming the metal matrix composite includes forming a plurality of grooves in the matrix. The reinforcement is located in and retained in the grooves with a binder/glue prior to the HIP or VHP operation. One limitation associated with the later approach is the increased risk of contamination associated with the out gassing during removal of the binder/glue.
While there are numerous prior techniques for forming metal matrix composite preforms, there remains a need for further development in this field of technology. The present invention satisfies this need, and others, in a novel and non-obvious way.